Method for producing isocyanate

Abstract

Isocyanates, preferably diisocyanates and polyisocyanates of the diphenylmethane series (MDI), are produced by reaction of amines dissolved in a solvent with phosgene in the same solvent to form the corresponding isocyanates. Hydrogen chloride and excess phosgene are subsequently removed from the reaction mixture to obtain a crude isocyanate-containing solution. Subsequently, the crude isocyanate-containing solution is separated by distillation into isocyanates and solvent. The solvent is recycled and used for the production of solutions of the amines and of phosgene. The solvent being recycled is treated to reduce the phosgene and diisocyanate contents before being used for the production of the solution of the amine.

Description

Technical field

[0001] The present invention relates to a method for producing isocyanates (preferably diisocyanates and polyisocyanates (MDI) of the diphenylmethane series). The method comprises reacting amines dissolved in a solvent with phosgene to form the corresponding isocyanates, and then removing Hydrogen chloride and excess phosgene, then the crude isocyanate-containing solution obtained in this way is separated into isocyanate and solvent by distillation, and the solvent is recycled to produce a solution of amine and phosgene, wherein the solvent part used to produce the amine solution contains a small amount Phosgene and diisocyanate. Background technique

[0002] The production of isocyanates by reacting primary amines with phosgene is a well-understood prior art. A solution of an amine in a suitable solvent is usually reacted with a solution of phosgene in the same solvent. For example, the production of organic isocyanates from primary amines and phosgene is describ...

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